Solid propellant rocket motors have been designed in many sizes and shapes. The rocket motor includes a motor case which serves as a container for the solid propellant charge referred to as a grain. The general practice in manufacturing solid propellant rocket motors includes providing a motor case liner which insulates the rocket motor case from the burning propellant grain. The grain is required to be securely bonded to the liner to ensure that propellant grain break-up does not take place as a result of the acceleration forces which are built up during the burning phase of the rocket motor. If the grain is not adequately bonded, separation of the liner and propellant can occur, then burning will take place on the liner side of the propellant. This would result in a greatly increased burning surface and motor malfunction due to overpressurization. wherever the strength of the bond between the liner and the grain is inadequate, due to improper mechanical adhesion, a problem area exists. This would cause the development of unequal stresses in the grain during storage which can result in cracking of the propellant grain or separation of the propellant from the liner. Therefore, it is essential that bonding of the grain to the liner is uniform, and that the bond has adequate mechanical adhesion. It is, also, essential that the liner be adequately bonded to the rocket motor case.
A problem in the prior art liners relates to the tendency of the liner material, after cure, to have too smooth an interior surface, and, thereby, result in poor mechanical adhesion between the grain and the liner regardless of whether the grain is cast-in-place and cured, or whether the grain is first cured, and then bonded to the liner after the grain is inserted in the motor case.
An object of this invention is to provide a flexible highly-adhesive rocket motor case liner insulation material which is curable to yield a wrinkled interior surface and thus provide a much larger surface area for bonding to the propellant than is the case with state-of-the-art propellant-liner systems.
Another object of this invention is to provide a flexible, highly-adhesive rocket motor case liner insulation material that is compounded of ingredients that have low signature characteristics, and which are compatible with cast-in-place solid propellant compositions which form a stronger mechanical adhesive bond because the propellant penetrates into the wrinkled surface because of the increased surface for bond formation, and because of the mechanical interlocking of the propellant within the wrinkles of the liner.
A further object of this invention is to provide a flexible, highly-adhesive rocket motor case liner insulation material which has good bonding characteristics to different types of rocket motor case materials, of the monolithic types (steel, titanium, etc.) or filamentous type (fiberglass composite, graphite composite, etc.).